Upgrading to version 12 - Missing CSS 404 not found

ERPNext
,
2

Ok so I fixed all that by install yarn/rollup manually.

The updates were successful and I am now able to run the following:

$bench switch-to-branch version-12 --upgrade
$ bench update --patch

But the when I try to access the site, it throws the following errors:
404 Not Found : assets/css/frappe-web-b4.css
404 Not Found : /assets/js/bootstrap-4-web.min.js

And an error on the console:

Uncaught TypeError: $(...).dropdown is not a function
    at HTMLDocument.<anonymous> (frappe-web.min.js:1)
    at HTMLDocument.dispatch (jquery.min.js:3)
    at HTMLDocument.r.handle (jquery.min.js:3)
    at Object.trigger (jquery.min.js:4)
    at HTMLDocument.<anonymous> (jquery.min.js:4)
    at Function.each (jquery.min.js:2)
    at n.fn.init.each (jquery.min.js:2)
    at n.fn.init.trigger (jquery.min.js:4)
    at HTMLDocument.<anonymous> (frappe-web.min.js:1)
    at i (jquery.min.js:2)

Thanks for your help.